Inserter for expanding body tissue

ABSTRACT

An elongate inserter has a distal end releasably connected to an expandable device for expanding body tissue and a proximal end including a trigger actuator. The expandable device comprises a superior endplate and an inferior endplate that are movable in an expansion direction relative to each other between opposing tissue surfaces of a body. The inserter includes a lifting platform comprising ramp surfaces that upon operation of the trigger actuator cooperatively engage complementary surfaces of expansion structure within the device to cause the superior and inferior endplates to move relatively away from each other. A driver is supported by the inserter for pushing an insert between the superior and inferior endplates after expansion of the device.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/736,832, filed Jun. 11, 2015, now U.S. Pat. No. 9,439,783, which is acontinuation-in-part application of U.S. application Ser. No.14/474,639, filed Sep. 2, 2014, now U.S. Pat. No. 9,114,026, whichclaims the benefit of U.S. Provisional Patent Application No.61/948,660, filed Mar. 6, 2014, each of which is herein incorporated byreference in its entirety.

FIELD OF THE INVENTION

The subject invention relates generally to the field of surgery, andparticularly to surgical devices, instruments and methods of using thesame.

BACKGROUND OF THE INVENTION

A variety of physical conditions involves two bodily tissue surfacesthat, for treatment of the condition, need to be separated from oneanother and supported away from one another. Such tissue expansion maybe to gain exposure to select tissue structures, to apply a therapeuticpressure to select tissues, to return tissue structures to theiranatomic position and form, or in some cases to deliver a drug or growthfactor to alter, influence or deter further growth of select tissues.Depending on the condition being treated, the tissue surfaces may beopposed or contiguous and may be bone, skin, soft tissue, or acombination thereof.

One particular device for treating these conditions by distracting andsupporting tissue surfaces simultaneously is described in U.S. Pat. No.6,595,998, entitled “Tissue Distraction Device”, which issued on Jul.22, 2003 (the '998 Patent). Other examples of such tissue distractingand supporting devices that are used for achieving spinal interbodyfusion are described in U.S. Pat. No. 7,931,688 entitled “ExpandableInterbody Fusion Device”, which issued on Apr. 26, 2011 (the '688Patent), and U.S. Pat. No. 7,967,867 entitled “Expandable InterbodyFusion Device”, which issued on Jun. 28, 2011 (the '867 Patent). The'998 Patent, the '688 Patent and the '867 Patent each disclosessequentially introducing in situ a series of elongate inserts referredto as wafers in a percutaneous approach to incrementally distractopposing vertebral bodies to stabilize the spine and correct spinalheight, the wafers including features that allow adjacent wafers tointerlock in multiple degrees of freedom. The '998 Patent, the '688Patent and the '867 Patent are assigned to the same assignee as thepresent invention, the disclosures of these patents being incorporatedherein by reference in their entirety.

An issue that has arisen regarding such interbody fusion devices thatuse inserts or wafers to incrementally expand such devices is thedetermination of when full expansion has been achieved as a result ofligamentotaxis and no further inserts may be inserted. It is thereforedesirable for a surgeon to know when a sufficient number of inserts hasbeen introduced to stabilize the spine and correct spinal height andwhether any additional inserts may be introduced. One approachaddressing this issue is described in commonly assigned U.S. Pat. No.8,828,019, entitled “Inserter for Expanding an Expandable InterbodyFusion Device”, issued on Sep. 9, 2014 (“the '019 Patent”) andincorporated herein by reference in its entirety.

Accordingly, there is a need for an improved expandable interbody fusiondevice and inserter to expand and insert such a device, including thecapability to determine when proper expansion of the device has beenachieved and no further inserts may be introduced.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an inserter for expanding anexpandable device to expanding body tissue and for sequentiallyinserting one or more inserts after each incremental expansion of thedevice. A further object is the provision of the capability of theinserter to allow a surgeon to determine that suitable expansion hasbeen reached and that no additional inserts may be inserted.

DESCRIPTION OF THE FIGURES

FIG. 1a is a top perspective of an apparatus including an inserterreleasably attached to an expandable spinal interbody fusion device inaccordance with an embodiment of the present invention, the expandableinterbody fusion device being unexpanded.

FIG. 1b is a side elevation view of the apparatus of FIG. 1 a.

FIG. 1c is a top plan view of the apparatus of FIG. 1 a.

FIG. 2 is an enlarged view of the distal portion of the apparatus ascircled in FIG. 1 c.

FIG. 3 is an exploded top perspective view of the distal end of theinserter and device of FIG. 1 a.

FIG. 4a is a top perspective view of an insert used in the expandablespinal interbody fusion device of FIG. 1 a.

FIG. 4b is a top plan view of the insert of FIG. 4 a.

FIG. 4c is a longitudinal cross-sectional view of the insert as seenalong viewing lines IV-IV of FIG. 4 b.

FIG. 4d is a bottom plan view of the insert of FIG. 4 a.

FIG. 4e is a distal end elevation view of the insert of FIG. 4 a.

FIG. 5a is a top perspective view of an elevator used in the expandablespinal interbody fusion device of FIG. 1 a.

FIG. 5b is a top plan view of the elevator of FIG. 5 a.

FIG. 5c is a longitudinal cross-sectional view of the elevator as seenalong viewing lines V-V of FIG. 5 b.

FIG. 5d is a bottom plan view of the elevator of FIG. 5 a.

FIG. 6 is a cross-sectional view of the inserter and device of FIG. 1aas seen along viewing lines VI-VI of FIG. 1 c.

FIG. 6a is an enlarged view of the encircled portion A of FIG. 6.

FIG. 7a is a cross-sectional view of the distal end of the inserter anddevice as seen along viewing lines A-A of FIG. 2 with the expandabledevice unexpanded.

FIG. 7b is a cross-sectional view of the distal end of the inserter anddevice as seen along viewing lines B-B of FIG. 2 with the expandabledevice unexpanded.

FIG. 8 is a top partial perspective view of the distal end of the lowertrack of the inserter showing a lifting platform and the elevator of theexpandable device in the position depicted in FIGS. 7a and 7 b.

FIG. 9 is a cross-sectional view of the lifting platform and elevator asseen along viewing lines IX-IX of FIG. 8.

FIGS. 10a and 10b are views similar to FIGS. 7a and 7b with the liftingplatform having been distally moved to a position lifting the elevatorand expanding the expandable device and a first insert partiallyentering the expanded device.

FIG. 11 is a view similar to FIG. 7a showing the first insert insertedinto the expanded expandable device.

FIGS. 12a and 12b are views similar to FIGS. 10a and 10b with thelifting platform having been moved distally to a position lifting theelevator and the first insert to further expand the expandable devicewith a second insert partially entering the expanded device.

FIGS. 13a and 13b are views of the expandable device expanded as shownin the views of FIGS. 12a and 12b with the second insert having beenfurther distally moved to a position moving the elevator away from thefirst insert and creating a space for the insertion of the secondinsert.

FIG. 14 is a view similar to the view of FIG. 11 showing the first andsecond inserts inserted into the expanded expandable device.

FIG. 15 is a cross-sectional view as seen along the viewing lines XV-XVof FIG. 14.

FIG. 16 is a proximal perspective view of the expanded spinal interbodyfusion device with a guide pin releasably connected thereto subsequentto the inserter having been detached from the guide pin with inserts notbeing shown for clarity.

FIG. 17 shows a vertebral body having a compression fracture displacingits superior and anterior edge.

FIG. 18 shows a vertebral body, following treatment of a compressionfracture.

FIG. 19 illustrates a plan view of an insertion apparatus according toanother embodiment of the invention, placed within a vertebral body ofFIG. 17, shown in cross-section.

FIG. 20 shows a side view of the insertion apparatus of FIG. 19 beingdeployed within a vertebral body, shown in sectional view.

DESCRIPTION OF THE EMBODIMENTS

For the purposes of promoting and understanding of the principles of theinvention, reference will now be made to the embodiments illustrated inthe drawings and described in the following written specification. It isunderstood that no limitation to the scope of the invention is therebyintended. It is further understood that the present invention includesany alterations and modifications to the illustrated embodiments andincludes further applications of the principles of the invention aswould normally occur to one skilled in the art to which this inventionpertains.

The invention provides a combination of an implantable expansion andsupport device and instrumentation to place the device into body tissue.The application of the invention as a spinal implant in spinal interbodyfusion is detailed initially. Turning now to FIGS. 1a-c and FIGS. 2-3,an apparatus 1 for use in spinal interbody fusion is shown. Apparatus 1comprises an expandable spinal interbody fusion device 10 and aninserter 100. The inserter 100 is an instrument used for inserting thedevice 10 into an intradiscal space between opposing vertebral bodies ofa spine, expanding the device in situ and for inserting inserts into theexpanded device 100. As shown in FIG. 3, the expandable interbody fusiondevice 10 includes a first element, such as superior endplate 12, asecond element, such as inferior endplate 14, at least one insert 16 andexpansion structure defined by an elevator 18, as will be detailedhereinbelow. The height, H, across the superior and inferior endplates12, 14 in the unexpanded condition as illustrated in FIG. 1b is lessthan the normal anatomic height of a typical intradiscal space. Theinvention contemplates expanding the interbody fusion device 10 by theinserter 100 to ultimately restore the normal anatomic height of thedisc space and thereafter inserting one or more inserts, such asinterlocking inserts 16, as will be described, to form a stack ofinserts 16 between the expanded superior endplate 12 and inferiorendplate 14.

The superior endplate 12 as shown in FIGS. 3 and 15 is elongate andcomprises a hub 20 having pair of side surfaces 22 and 24 extendinglongitudinally on each side of the hub 20 and a pair of end surfaces 26and 28 extending respectively at the proximal rear end and the distalfront end of the superior endplate 12. The hub 20 is sized andconfigured to fit within a cavity of the inferior endplate 14 fortelescoping movement therewithin, as will be described. The lowersurface 30 of the hub 20 (FIG. 15) includes a shaped configurationdefined by a recessed interior surface 31 and insert interlockingfeatures 32 that are substantially identical to the interlockingfeatures on the lower surface of each insert 16, as will be described.The hub 20 defines a series of grooves 34 as shown in FIG. 3 extendingalong each side surface 22 and 24 thereof that are configured to engageribs 36 projecting interiorly of the inferior endplate 14. Thisengagement temporarily holds the superior and inferior endplatestogether in the direction of expansion as the device 10 is introducedinto the intradiscal space to be distracted.

As shown particularly in FIGS. 2-3 and 15, the superior endplate 12includes a graft chamber defined by an opening 38 extending through theupper outer surface 12 a and the lower interior surface 31. Inaccordance with one arrangement, the superior endplate 12 is formed of abiocompatible polymer such as polyethylethylketone (PEEK). PEEK is usedin fusion applications for its combination of strength,biocompatibility, and elasticity which is similar to human bone. Othercomposites may include derivatives of PEEK such as carbon fiberreinforced PEEK and PEKK, respectively. In a particular aspect, thesuperior endplate 12 may further include an upper endcap that definesthe outer surface 12 a. The endcap may be a separate plate formed ofmaterial for the promotion of bone growth, such as titanium, and may beattached to the endplate 12 with suitable conventional techniques. As analternative, the upper surface 12 a may be defined by a coating of asuitable layer of bone growth promotion material, such as titanium,which may be deposited by conventional techniques.

The inferior endplate 14 of the interbody fusion device 10 as shown inFIGS. 2-3 and 15 is elongate and comprises a pair of opposing spacedapart sidewalls 40 and 42 extending along the longitudinal direction andprojecting upwardly from the lower outer surface 14 a. A pair of spacedapart end walls 44 and 46 extend laterally across the device and projectupwardly from outer surface 14 a. Rear end wall 44 is disposed at therear or proximal end of the device 10 and front end wall 46 is disposedat the front or distal end of the device 10. The side walls 40, 42together with rear end wall 44 and front end wall 46 form an open,upwardly facing fully bounded interior cavity 48 as shown in FIG. 3. Theinterior cavity 48 is sized and configured to receive the superiorendplate 12 including the hub 20 in relatively close fit between theside walls 40 and 42 and the end walls 44 and 46 of the inferiorendplate 14 in a non-expanded condition as shown in FIGS. 1a-b . The hub20 of superior endplate 12, as well as the entire stack of inserts 16,remains fully contained within the inferior endplate 14 duringtelescoping expansion of the device 10 as shown in FIGS. 15 and 16,contributing to the torsional strength of the expanded device 10.

The inferior plate 14 as shown in FIG. 16 defines a fully bounded insertchannel 50 extending through the rear end wall 44 in communication withinterior cavity 48 and through which the inserts 16 are introduced. Theinferior endplate 14 includes a pair of opposite ledges 52 that define asupport surface on which each insert 16 is supported as it introducedinto the insert channel 50, as will be described. The inferior endplate14 further includes a lower inner support surface 54 on which theelevator 18 is supported. Lower inner surface 54 defines the bottomsurface of the cavity 48 and a recess 53 bounded laterally by oppositeledges 52. Inserts are introduced sequentially into channel 50 on top ofelevator 18, as will be described. The rear end wall 44 further definesa threaded connection opening 56 (FIG. 7a ) for threaded releasablereceipt of a guide pin for use in the introduction of inserts 16 and inthe delivery of bone graft material into the device 10, as will also bedescribed. Rear end wall 44 may also additionally include a pair ofbilateral openings, such as notches 58, adjacent the sidewalls 40 and 42for use in releasably attaching the inserter 100 to the device 10 forthe establishment of a rigid connection to the device 10 for insertioninto the intradiscal space.

As shown particularly in FIGS. 3 and 15, the inferior endplate 14includes a graft chamber defined by an opening 60 extending through thelower outer surface 14 a and the lower inner surface 54 in communicationwith cavity 48. In accordance with one arrangement, the inferiorendplate 14 is formed of a material different from the material of thesuperior endplate 12. In this aspect, the inferior endplate 14 may beformed of a biocompatible metal, such as titanium, for its strengthproperties. Titanium is chosen for strength, biocompatibility,processing capability, and fluoroscopic imaging properties(radiolucency). Other alternative materials include cobalt chrome,stainless steel (both stronger than titanium but much less radiolucent),or biocompatible ceramics such as silicon nitride or zirconia, which areradiolucent. Titanium and silicon nitride have demonstrated goodapposition to bone and superiority to PEEK. In this regard whereinferior endplate 14 is formed of titanium, the lower outer surface 14 awould provide for the promotion of bone growth. Lower outer surface 14 amay also, however, be coated with a suitable layer of bone growthpromotion material, such as titanium, and deposited in a conventionalmanner so as to match the roughness/porosity of the superior endplateouter surface 12 a.

Where inferior endplate 14 is formed of titanium or other suitable metalthat is radiopaque, windows 62 may be formed through sidewalls 40 and 42and/or through front endwall 46 as shown in FIGS. 3 and 16 so as toallow visual observation of bony through growth by suitable imagingtechniques, such as fluoroscopy. Further details of interbody fusiondevice 10 are described in commonly assigned U.S. Pat. No. 8,900,312,patent application Ser. No. 13/795,054 entitled “Expandable InterbodyFusion Device with Graft Chambers”, filed on Mar. 12, 2013 (“the '312Patent”) and incorporated herein by reference in its entirety.

Details of the interlocking insert 16 are shown in FIGS. 4a-e . Theinsert 16 comprises an elongate and generally flat body 200 having anupper surface 202 and a lower surface 204, both of which are generallyplanar and substantially parallel so that the inserts 16 can form astable stack within the interbody fusion device 10 upon expansion.Insert 16 includes a trailing rear proximal end 206 and a leading frontdistal end 208. The body 200 is formed to have a generally U-shaped,horseshoe configuration, with a pair of spaced opposing arms 212 and 214projecting rearwardly from a base 205 and defining a rearwardly facinggenerally U-shaped opening 216 extending through the rear end 206 andthrough upper surface 202 and lower surface 204. A surface 218 betweenthe upper surface 202 and the lower surface 204 at the base 205 ofopening 216 defines a pushing surface for receipt of a driver ofinserter 10, as will be described. The opening 216 at the rear end ofeach insert 200 is provided to allow bone graft material to flow intothe device 10 through the insert openings 216 and into the openings 38and 60 extending through the superior endplate 12 and the inferiorendplate 14, respectively. The front distal end includes an inclinedsurface 208 a extending upwardly from and communicating with lowersurface 204.

The insert 16 includes several features for interlocking engagement tothe hub 20 and to adjacent inserts 16 in a complementary cooperativeinterlocking mating interface. One particular feature includes a lockingelement defined by a resiliently deflectable prong 220 that projectsoutwardly above the upper surface 202 at the insert base 205 in thedirection of expansion of device 10. A complementary locking surface 222is defined in the lower surface 204 of the insert 200 for resilientengagement with the prong 220 of a subsequent insert 16 as each insert16 is inserted into device 100 to form a stack. The lower surface 204 ofeach insert body 200 includes a shaped configuration defined by arecessed interior surface 204 a and insert interlocking featuresdefining a T-slot configuration 224 for mating with a T-barconfiguration 226 on the upper surface 202 of a successive insert 16.While one locking element is shown, it should be appreciated that morethan one locking element may be formed, the structure and function ofthe prongs 220 and locking surfaces 222 being more fully described inthe '312 Patent. However, unlike the inserts described in the '321Patent, the inserts 16 described herein do not function to assist in theseparation of superior endplate 12 and inferior endplate 14 or anysubsequent inserts 16 inserted into interbody fusion device 16, as thatlifting function is provided by inserter 100 in conjunction withelevator 18. It is contemplated that the inserts 16 described herein beformed of a biocompatible material that is sufficiently rigid to form asolid stack as the successive inserts are inserted into the device.Thus, in one specific embodiment, the inserts are formed of PEEK or acarbon-fiber reinforced PEEK, or similar polymeric material.

Turning now to FIGS. 5a-d , details of the elevator 18 are shown. Theelevator 18 comprises an elongate and generally flat body 300 having anupper surface 302 and a lower surface 304, both of which are generallyplanar and substantially parallel. The elevator 18 has a thicknessbetween upper surface 302 and lower surface 304 that is slightly greaterthan the thickness of insert 16. As such, when as noted below thethickness of an insert 16 is, for example, 1.0 mm, the thickness ofelevator 18 may be 1.03 mm. Elevator 18 includes a trailing rearproximal end 306 and a leading front distal end 308. The elevator body300 is formed to have a generally U-shaped, horseshoe configurationsimilar to the configuration of insert 16. Elevator body 300 includes apair of spaced opposing arms 312 and 314 projecting rearwardly from abase 305 and defining a rearwardly facing generally U-shaped opening 316extending through the rear end 306 and through upper surface 302 andlower surface 304. Base 305 has a rearwardly facing surface 305 a thatcommunicates with opening 316. The opening 316 at the rear end ofelevator 18 is provided to allow bone graft material introduced into thedevice 10 to flow through the insert openings 216 of inserts 16 and intothe openings 38 and 60 extending through the superior endplate 12 andthe inferior endplate 14, respectively. The rear proximal end 306includes an inclined surface 312 a and 314 a, respectively at the freeend of each arm 312 and 314 extending downwardly from and communicatingwith the upper surface 302. The rear proximal end 306 further includesan inclined lifting surface 312 b and 314 b, respectively at the freeend of each arm 312 and 314 extending upwardly from and communicatingwith the lower surface 304. The front distal end 308 includes adjacentbase surface 305 a an inclined lifting surface 308 a extending upwardlyfrom and communicating with lower surface 304. The inclined liftingsurfaces 312 b, 314 b and 308 a are angled in the same direction withapproximately equal angles. The lifting surfaces 312 b, 314 b and 308 adefine inclined ramps with multiple points of contact for cooperativecontact with complementary surfaces of an expansion component on theinserter 100 for lifting elevator 18, as will be described. Inclinedsurface 308 a is generally centrally located along the elongate axis ofelevator, while surfaces 312 b and 314 b are spaced bilaterally. Thus,lifting surfaces 308 a, 312 b and 314 b define three triangulated pointsof contact. Lastly, elevator has a hole 310 extending though theelevator base 305 and the upper surface 302 and the lower surface 304.Hole 305 is sized to receive a post on the inferior endplate 14, as willbe described. In one specific embodiment, the elevator 18 is formed oftitanium alloy, type 2, which may be anodized for lubricity. Othermaterials, such as PEEK, may also be used as the material for elevator18.

Turning again now to FIGS. 1a-c and FIG. 3, details of the inserter 100are described. Inserter 100 is elongate having a distal end 100 a and ata proximal end 100 b a frame 101. A trigger actuator 102 to effectexpansion of device 10 and insertion of inserts 16 into device 10 afterexpansion is attached to frame 101 at the proximal end 100 b ofinserter. A plurality of inserts 16 are movably supported in a lineararray on track 104 for individual successive insertion into device 10.Track 104 supports at least one insert 16 and may, for example, supportan array of five inserts 16, although fewer or more inserts 16 may besupported as desired.

The distal end 100 a is shown in exploded detail in FIGS. 3. Theinserter 100 includes an elongate lower track 104 and an upper trackcover 106, the cover 106 being slidably joined to track 104. Lower track104 is configured as an upwardly facing open channel and is movablysupported by frame 101. Cover 106 is fixedly secured to frame 101. Anelongate guide pin 108 is supported by frame 101 and within an opening110 extending lengthwise through the cover 106. The distal end 108 a ofthe guide pin 108 is threaded for releasable threaded engagement intoopening 56 in the proximal rear end wall 44 of the inferior endplate 14.The proximal end of guide pin 108 is provided with a threaded knob 112for compressing and releasably attaching the frame 101 and cover 106 andthereby the inserter 100 to the device 10. The track cover 106, in onearrangement, includes a pair of opposing tabs 114 that engagecorresponding notches 58 in rear wall 44 of inferior endplate 14 toassist in rigidly securing the inserter 100 to the device 10. It shouldbe appreciated that other securement structure may be used to releasablyattach the inserter 100 to the device 10. Track 104, in one embodiment,is formed of stamped stainless steel and cover 106 is an extrudedaluminum alloy. Stainless steel or strong reinforced plastic could alsobe used for cover 106.

The track 104 at the distal end 100 a of the inserter 100 supports anexpansion component defined by an axially translatable lifting platform116 attached to track 104 for common axial movement therewith tocooperatively contact elevator 18 for expanding the device 10. Thelifting platform 116 is elongate and generally flat having an uppersurface 118 and a lower surface 120, both of which are generally planarand substantially parallel (FIG. 15). The lifting platform 116 has athickness between upper surface 118 and lower surface 120 that isdimensioned to be the same as the thickness of elevator 18, i.e.,slightly greater than the thickness of an insert 16. Track 104 andthereby lifting platform 116 are supported by the inserter 100 forreciprocating axial movement in projecting and retracting directions.Track 104 includes a lower surface 122 on which inserts 16 are movablysupported in a linear array. The proximal end of the track 104 iscoupled to the trigger actuator 102 to effect such projecting andretracting directions, as will be described.

Lifting platform projects axially outwardly from track 104 and includesat its free distal end an inclined lifting surface 116 a extendingdownwardly from and communicating with upper surface 118. At a locationspaced proximally of lifting surface 116 a, lifting platform furtherincludes a pair of laterally spaced inclined surfaces 116 b and 116 c.The inclined lifting surfaces 116 a, 116 b and 116 c are angled in thesame direction with angles approximately equal to the anglesrespectively of inclined lifting surfaces 312 b, 314 b and 308 a ofelevator body 300. Inclined surfaces 116 a, 116 b and 116 c defineinclined ramps with multiple complementary points of contact forcooperative contact with elevator 18. Inclined surface 116 a isgenerally centrally located along the elongate axis of lifting platform116, while surfaces 116 b and 116 c are spaced bilaterally. Thus,lifting surfaces 116 a, 116 b and 116 c define three triangulated pointsof contact that are located and spaced to cooperatively contact liftingsurfaces 308 a, 312 b, and 314 b, respectively during movement oflifting platform 116 in the projecting direction. Lifting platform 116,particularly inclined surfaces 116 a, 116 b and 116 c, may be coated orotherwise include a suitable lubricant to facilitate sliding contactwith elevator 18 for expansion of device 10. Where lifting platform 116is made of stainless steel, for example, such lubricant may include amolybdenum disulfide (MoS₂) material.

Still referring to FIG. 3, inserter 100 further supports at its distalend 100 a a driver 124 for axial translational movement within track104. The proximal end 124 a (FIG. 6) of driver 124 is coupled to triggeractuator 102 to effect translational movement of the driver 124, as willbe described. The distal end of driver 124 comprises a pushing surface124 b sized and configured to enter into the opening 216 of an insertbody 200 to engage pushing surface 218 and push the insert 16 from track104 into the device 10 upon axial distal movement of driver 124.

With further reference still to FIG. 3, inserter 100 comprises aflexible graft shield 128 projecting distally from track cover 106.Graft shield 128 is supported at one end 128 a in a cantilevered mannerwith an opposite end 128 b being unsupported and free to flex. Graftshield 128 is elongate and generally flat and is sized and configured tosubstantially block communication between the opening 38 through thesuperior endplate 12 and inserts 16 slidably inserted into device 10. Aswill be described, graft shield 128 is configured to extend into device10 through channel 50 between the superior endplate 12 and the expansionstructure adjacent the lower interior surface 31 of the superiorendplate 12.

Turning now to FIGS. 6 and 6 a, the details of the trigger actuator 102of the inserter 100 and its function are described. Trigger actuator 102comprises a pair of hand grips 132 and 134 biased apart by a leaf spring136. Hand grip 132 is fixedly secured to frame 101 of inserter 100. Handgrip 134 is pivotally connected to frame 101 at pivot point 138 and ismovable toward hand grip 132 against the bias of leaf spring 136 bymanual pressure. Hand grip 134 has internal gear teeth 140 thatinterface with a small diameter gear 142 that is rigidly coupled to alarge diameter gear 144. Large diameter gear 144 interfaces with a gearrack 146 rigidly coupled to the proximal end 124 a of the driver 124.The gear mechanism is sized to provide the appropriate translation ofdriver 124 in the projecting direction as trigger actuator 102 isactuated. Driver 124 is releasably coupled to the proximal end 104 a oftrack 104 via a ball clutch 148. Bilateral ball bearings 150 residing inblind holes 152 and 153 within the driver 124 and track 104 respectivelyare biased partially within the track 104 by compression springs 154.Blind holes 153 within track 104 have a partial opening in the floorthereby exposing approximately half of the lower hemisphere 150 a of theballs 150. When the coupled driver 124 and track 104 have achievedsufficient axial translation in the projecting direction to expand thedevice 10, the exposed portions 150 a of the balls 150 contact bilateralfixed ramps 156 ejecting them from the blind holes 152 within track 104thereby decoupling the track 104 and driver 124. Continued triggeractuation advances the driver 124 independently distally of track 104.Frame 101 and hand grips 132, 134 are all formed of stainless steel in aparticular arrangement, although other materials, such as aluminumalloys and plastics may also be used.

For the purpose of returning the track 104 to its original position inthe retracting direction a cam 158 and a return gear (not shown)rotatable about an axis 160 are provided. The return gear interfaceswith the large diameter gear 144. The cam 158 is rigidly coupled toreturn gear and is positioned to contact a notch 162 in the track 104after an insert 16 has been partially inserted into the device 10.Further trigger actuation returns the track 104 to its original positionwhile further inserting the insert 16. When full trigger actuation isachieved, the driver 124 and hand grips 132/143 are returned under thebias of the leaf spring 136, and the ball clutch 148 is re-engaged. Atwo way ratchet mechanism (not shown) prevents unwanted motion in thewrong direction. Thus, during a single stroke operation of triggeractuator 102, the elevator 18 is lifted by lifting platform 116 upontranslational movement of track 104 and lifting platform 116 in theprojecting direction, driver 124 pushes an insert 16 into the expandeddevice 10, track 104 and thereby lifting platform 116 are retracted inthe retracting direction, and finally driver 124 is retracted fromdevice 10. Such single stroke of operation is initiated when hand grips132/134 are in the starting position of FIG. 6 and is completed whenhand grips 132/134 are returned to the starting position under the biasof leaf spring 136.

Turning now to FIGS. 7a-b and 8-9 the assembly of the device 10 and theinserter 100 is described. The superior endplate 12 and the inferiorendplate 14 are assembled in an unexpanded condition to the inserter 100with the superior endplate 12 residing fully within cavity 48 ofinferior endplate 14. In such condition superior endplate 12 and theinferior endplate 14 are provisionally held together in the direction ofexpansion by the engagement of ribs 36 and grooves 34, as describedhereinabove. The inserter 100 is releasably attached to the device 10upon threaded engagement of the guide pin 108 into threaded opening 56in the proximal rear end wall 44 of the inferior endplate 14. Graftshield 128 extends into device 10 through channel 50 between thesuperior endplate 12 and the elevator 18 adjacent the lower interiorsurface 31 of the superior endplate 12. With the inserter 100 fixed tothe device 10, track 104 with joined lifting platform 116 and driver 124are axially translatable relative to the device 10 in the projecting andretracting directions. In this unexpanded condition, there are noinserts 16 in the device 10. Inserts 16 are supported on track 104.

The elevator 18 is supported on lower inner surface 54 within recess 53of inferior endplate 14 with the lateral width of elevator 18 beingclosely dimensioned to the opposite ledges 52 (FIG. 15). As such,lateral movement in a direction transverse to the direction of expansionis substantially constrained. In addition, inferior endplate 14 includesa post 14 b projecting upwardly from lower inner surface 54 towardsuperior endplate 12. Post 14 b slidably projects through the hole 310extending through the base 305 of elevator 18. Post 14 b substantiallyconstrains movement of elevator 18 in the axial direction while theclearance in hole 310 allows free movement of elevator 18 in thedirection of expansion along post 14 b as shown by the arrow 130 in FIG.7a . As such, elevator 18 is captively supported within inferiorendplate 14 and is independently movable along the direction ofexpansion toward and away from each of the superior endplate 12 and theinferior endplate 14. However, with the inserter 100 attached to thedevice 10, elevator 18 is fixed in the axial direction relative to axialmovement of lifting platform 116.

In the position illustrated in FIGS. 7a-b and 8-9 lifting platform 116is in a retracted position relative to device 10 and elevator 18. Insert16, as seen in FIG. 7a , is disposed on track 104 exteriorly of andready for insertion into device 10. In this position the lower surface120 of lifting platform 116 is situated on lower inner surface 54 ofinferior endplate 14. Likewise lower surface 304 of elevator 18 issupported by lower inner surface 54 of inferior endplate 14. As such,lifting platform 116 and elevator 18 are on substantially the sameplane, with the upper surface 118 of lifting platform 116 beingsubstantially coplanar with the upper surface 302 of elevator 18.

In the condition shown in FIGS. 7a-b , apparatus 1 comprising unexpandeddevice 10 releasably attached to inserter 100 is ready for use ininserting device 10 into an intradiscal space between two opposingvertebral bodies. Prior to insertion, opening 38 through superiorendplate 12 may be pre-packed with a suitable bone graft material forthe promotion of fusion through device 10 to the opposing vertebralbodies. Graft shield 128 extends into device 10 through channel 50between the superior endplate 12 and the elevator adjacent the lowerinterior surface 31 of the superior endplate 12 defining a pocket forreceipt of the graft material. The free end 128 b of graft shield 128rests unattached on an interior ledge 12 b of superior endplate 12adjacent the distal end thereof. Opening 38 is therefore open adjacentouter surface 12 a of superior endplate 12 and closed by graft shield128 adjacent lower interior surface 31. As such, graft shield 128provides a barrier between the graft material and the elevator 18 andinserts 16 inserted into device 10 during expansion. Pre-packing of bonegraft material in opening 38 on graft shield 128 advantageously allowsfor less introduction of graft material in situ and provides moreassurance that sufficient graft material will be contained throughoutdevice 10 and into openings 38 and 60 through superior endplate 12 andinferior endplates 14 and a stress-loaded condition against opposingvertebral bodies. In addition, graft shield 128 provides a barriersubstantially preventing graft material within opening 38 from beingdisturbed during expansion and by substantially blocking graft materialfrom interfering with the expansion of device 10 or with the slidableinsertion of inserts 16 which may be impeded by graft material on thesliding interfacing surfaces.

At this point in the surgical procedure, inserter 100 is used to insertunexpanded device 10 into the intradiscal space. Device 10 may beimplanted into the spine posteriorly or posteriolaterally, eitherbilaterally or unilaterally, or in an anterior or lateral approachdepending upon the surgical indication and the surgeons preference. Oncedevice 10 is inserted in the intradiscal space in a suitable location,actuator 102 as described hereinabove is then operated. Initially duringthe stroke the track 104 with the attached lifting platform 116 anddriver 124 are translated axially together. Lifting platform 116 ismoved from the retracted position of FIGS. 7a-b to a projectingdirection whereby lifting platform 116 is moved further into device 10.During movement in the projecting direction, lifting surfaces 116 a, 116b and 116 c of lifting platform 116 contact cooperative lifting surfaces308 a, 312 b, and 314 b, respectively of elevator 18. The cooperativeengagement causes elevator 18 to move in the direction of expansion awayfrom lower inner surface 54 of inferior endplate 14 and toward superiorendplate 12. The upper surface 302 of elevator 18 contacts lowerinterior surface 31 of superior endplate 12 and elevator 18 slidablymoves in the direction of expansion along post 14 b toward superiorendplate 12 and away from inferior endplate 14 as shown in FIGS. 10a-b ,thereby expanding device 10. During this expansion, driver 124 continuesto push insert 16 proximately toward device 10. Upon completion ofexpansion of device 10, the clutch 148 in the actuator 102 releasestrack 104 and thereby lifting platform 116 while movement of driver 124continues in the distal direction. In this expanded condition, thedistal front end 208 moves freely into expanded device 10 throughchannel 50 such that the distal front end 208 of insert 16 is partiallyinserted into expanded device 10 between superior endplate 12 andinferior endplate 14 adjacent the proximal end of device 10, asillustrated in FIGS. 10a -b.

With insert 16 partially inserted in device 10, continued operation ofthe actuator 102 during the stroke causes cam 158 in the actuator 102 topull track 104 with lifting platform 116 proximally thereby movinglifting platform 116 in a retracting direction. With distal front end208 of insert 16 supporting superior endplate 12, continued proximalmovement of lifting platform 116 causes lifting surfaces 116 a, 116 band 116 c of lifting platform 116 to sufficiently disengage cooperativelifting surfaces 308 a, 312 b, and 314 b, respectively of elevator 18 toallow elevator 18 to move away in the direction of expansion fromsuperior endplate 12 and toward inferior endplate 14 along post 14 b andreturn to the position of elevator 18 shown in FIGS. 7a-b . As elevator18 returns to the position whereby the lower surface 120 of liftingplatform 116 is situated on lower inner surface 54 of inferior endplate14, a space like space 64 described hereinbelow is created between lowerinterior surface 31 of superior endplate 12 and upper surface 302 ofelevator 18. Such space is slightly greater than the thickness of aninsert 16 and is in direct communication with lower interior surface 31of superior endplate 12 and upper surface 302 of elevator 18. Duringcompletion of the stroke of actuator 102 driver 124 continues to moveaxially distally slidably pushing insert 16 fully into such space ofexpanded device 10, as shown in FIG. 11, with lower interior surface 204a of insert 16 facing and being in contact with upper surface 302 ofelevator 18. Driver 124 is retracted proximally to the original positionshown in FIGS. 7a-b when the hand grip 134 of actuator 102 is releasedand the clutch 148 is reengaged.

During insertion of insert 16 into device 10, the interlocking featuresdescribed hereinabove on the upper surface 202 of insert 16cooperatively interlock with the complementary interlocking features 32on the lower surface 30 of superior endplate 12. Upon completion ofinsertion of insert 16, opening 216 of insert 16 is at least partiallyaligned with opening 38 of superior endplate 12 and opening 60 ofinferior endplate 14. Once inserter 100 is removed from the expandeddevice upon completion of the surgical procedure, openings 216, 38 and60 will all be in at least partial alignment and communication with eachother.

In the event the surgeon determines that additional inserts 16 arerequired in order to provide proper correction of the height of theintradiscal space, actuator 102 may be operated to insert one or moreadditional inserts 16 in the same manner as described with respect tothe insertion of first insert 16. FIGS. 12a-b show device 10 with oneinsert 16 having been inserted and a second insert 16 partiallyintroduced after device 10 has been further expanded by elevator 18 uponlifting by the lifting platform 116 in the same process as describedwith respect to FIGS. 10a-b . As the second insert 16 enters the furtherexpanded device 10, the cam 158 in the actuator 102 as described abovepulls lifting platform 116 proximally in a retracting direction,sufficiently disengaging lifting surfaces 116 a, 116 b and 116 c oflifting platform 116 from cooperative lifting surfaces 308 a, 312 b, and314 b, respectively of elevator 18 to allow elevator 18 to freely returnto inner surface 54 of inferior endplate 14. However, in the eventelevator 18 fails to fully or partially return to such position, duringcontinued pushing of second insert 16 into device 10 by driver 124, theinclined surface 208 a at the front distal end 208 of second insert 16contacts inclined surfaces 312 a and 314 a, respectively at the upperfree end of each arm 312 and 314 of elevator 18, as shown in FIGS. 13a-b, to urge elevator 18 toward and against inner lower surface 54 of theinferior endplate 14 creating a space 64 between lower interior surface204 a of the first insert 16 and upper surface 302 of elevator 18. Itshould be understood that the feature urging elevator 18 toward innerlower surface 54 of inferior endplate 14 functions during the insertionof first insert 16 as well as all subsequently inserted inserts 16.

Continued operation of actuator 102 will continue to move second insert16 until fully inserted shown in FIG. 14. During insertion of secondinsert 16 into device 10, the interlocking features describedhereinabove on the upper surface 202 of the second insert 16cooperatively interlock with the complementary interlocking features onthe lower surface 204 of the first insert 16. Upon completion ofinsertion of second insert 16, opening 216 of insert 16 is at leastpartially aligned with opening 216 of the first insert, opening 38 ofsuperior endplate 12 and opening 60 of inferior endplate 14, all ofwhich will be in communication upon removal of inserter 100. The secondinsert 16 being the lowermost insert resides on and is supported onledge 52 of inferior endplate 14 directly below and in interlockingcontact with first insert 16. Driver 124 is then again retractedproximally to the original position shown n FIGS. 7a-b when the handgrip 134 of actuator 102 is released and the clutch 148 is reengaged ina position for insertion of a third insert 16, if required.

When the intradiscal space has been expanded to its maximum anatomicextent as the spine reaches ligamentotaxis and the device 10 cannot befurther expanded, the surgeon will be able to determine such conditionby tactile feedback. Completion of a stroke of actuator 102 andinsertion is of an insert 16 into device 10 can only be achieved afterelevator 18 reaches its ultimate movement in the direction of expansiontoward superior endplate 12. As such, failure to compress hand grips132/134 in a manner to complete the actuator stroke will allow thesurgeon to recognize that ligamentotaxis has been reached and the properintradiscal height has been restored. Inasmuch as the insertion of aninsert 16 follows the expansion of device 10 upon full movement ofelevator 18 in the direction of expansion toward inferior endplate 14,incomplete insertion of an insert 16 may be avoided. The surgeon wouldthen terminate the procedure releasing hand grips 132/134, and thenremove the inserter 100 from the expanded device 10 by rotatablyremoving knob 112 from the proximal end of guide pin 108. As shown inFIG. 16, the guide pin 108 may remain releasably connected to expandeddevice 10 to serve as a locator for subsequent attachment to anapparatus containing suitable bone graft to assist in the delivery ofsuch material into a channel 50 of inferior endplate 14 through whichinserts 16 were inserted.

In accordance with certain specific applications of device 10, theoverall length of the device 10 as defined by the length of the inferiorendplate 14, is about 45 mm. The width of the device 10 is approximately19 mm. The height of the unexpanded device 10 of FIGS. 1a-c with thesuperior endplate 12 fully nested within the inferior endplate 14 isapproximately 8 mm. With the introduction of five inserts 16, each ofwhich has a thickness of approximately 1.0 mm, the height of device 10may be expanded from an unexpanded height of approximately 8 mm to anexpanded height of approximately 13 mm. Of course, the number of inserts16 may vary depending upon the particular surgery and the initial heightmay also be different. For example, device 10 may be formed to have aninitial unexpanded height of approximately 9 mm and with the addition offour inserts 16, each having a thickness of 1 mm, the height of device10 may be increased to approximately 13 mm. As such, it should beappreciated that these dimensions are only illustrative and that thedimensions of the device 10 and the number of inserts to be inserted andtheir thicknesses may vary depending upon the application.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same should be considered asillustrative and not restrictive in character. It is understood thatonly the preferred embodiments have been presented and that all changes,modifications and further applications that come within the spirit ofthe invention are desired to be protected. For instance, an inserterwith a graft shield, such as shield 128, may be used with expandablespinal interbody fusion devices having an expansion structure without anelevator 18 as described hereinabove. For example, an inserter with agraft shield 128 may be used with the expandable interbody fusion deviceshown and described in the '312 Patent referenced hereinabove whereinthe device is expanded upon introduction of a series of wafers. Shield128 may be used similarly as described herein to provide a barrierbetween a graft opening through one of the endplates, such as thesuperior endplate, and the wafers. Such a barrier would substantiallyprevent bone graft material pre-packed into such opening frominterfering with sliding receipt of such wafers during insertion andexpansion of the device. In addition, it should also be appreciated thatactuators other than trigger actuators, such as with threaded rotarymechanisms, may be used with the inserter 100 described herein.

While one use of the invention as described herein is as an expandablespinal interbody fusion device, the invention may also be used in anysituation where it is desirable to expand two tissue surfaces and tosupport such tissue surfaces after they have been separated. The tissuemay be bone, skin, soft tissue, or combinations thereof. Further, thesurfaces may be opposed surfaces of contiguous elements or surfaces ofopposed elements. Thus, in addition to being used as a spinal interbodyfusion device as set forth herein, the invention may also be used totreat vertebral compression fractures, for replacement of vertebralbodies (VBR), as a wedge opening high tibial osteotomy, tibialtuberosity elevation, as well as for treating other compressionfractures including, but not limited to tibia plateau fractures,calcaneous, distal tibial fractures, or distal radius (wrist) fractures.One method for treating these conditions includes distracting andsupporting the tissue surfaces simultaneously, as described in the '998Patent. The approach described herein, which includes expanding thetissue and then supporting the expanded tissue, may be used to treatthese same conditions. Such procedures may be performed percutaneouslythrough a cannula or other minimally invasive instrument or in an openprocedure.

The expansion device is now described in this section by its applicationas a spinal implant to vertebral compression fractures. FIG. 17 shows avertebral body 400 having a compression fracture displacing its superiorand anterior edge 402. FIG. 18 shows vertebral body 400 wherein theheight has been restored. FIG. 19 illustrates an extrapedicular approachto vertebral body 400 wherein an access cannula 404 is placed throughthe posterolateral wall 406 of vertebral body 400. Other approaches mayoptionally be used for placing a cannula into a vertebral body such as atranspedicular approach to the vertebral body wherein an access cannulamay be placed through the pedicle. In the extrapedicular approach, twocannulae 404 may be placed bilaterally, one on each side.

The procedure for the placement of access cannula 404 into verterbralbody 400 is more fully described in the '998 Patent, incorporated hereinby reference. Cannula 404 in this particular arrangement is preferablyrectangular in cross-section, although cannulae of other cross-sections,such as circular may be used. Further, cannula 404 may be of fixedconfiguration or expandable. Once access cannula 404 is in place, anexpandable device 10 supported by inserter 100 may be introduced intovertebral body 400 through cannula 404. This application of theinvention contemplates expanding expandable device 10 by the inserter100 from an unexpanded condition as shown, for example in FIG. 1b to theexpanded height as shown in FIG. 20 to ultimately reduce the vertebralcompression fracture and substantially restore the normal anatomicheight of vertebral body 400, inserting one or more inserts, such asinserts 16, as described herein, to form a stack of inserts 16 betweenthe expanded superior endplate 12 and inferior endplate 14 of expandabledevice 10. In the particular arrangement being described for vertebralcompression fracture reduction, expandable device 10 may have a lengthof approximately 25 mm, a width of approximately 10 mm, and anunexpanded height H of approximately 7 mm. The height H may be expandedby 5 mm and supported by the introduction of five inserts 16, as shownin FIG. 20, each insert 16 as described herein having a thickness of 1mm. It should be appreciated that the height H may be increased by otheramounts and more or less than five inserts used, and that device 10 maybe configured in other dimensions as set forth in the '998 Patent.

When the fracture is reduced as depicted in FIG. 18, or when thephysician determines that an adequate number of inserts 16 has beeninserted, the inserter 100 may be separated from device 10 and removedfrom cannula 404 while expanded device 10 remains within vertebral body400. Access cannula 404 is left in place. Suitable bone filler may beinjected into vertebral body 400 through cannula 404 to encapsulatedevice 10, provide weight bearing structure and increase stability ofvertebral body 400. Bone filler may flow through device 10 and theinsert column and out to the surrounding bone to interdigitate withcancellous bone.

It should therefore be understood that while various embodiments of theinvention have been presented herein, various changes, modifications andfurther applications may be made without departing from the spirit ofthe invention and the scope of the appended claims.

What is claimed is:
 1. An inserter for expanding an expandable device inbody tissue, said device being of the type comprising expansionstructure for expanding said device and having a graft chamber extendingtherethrough for the receipt of bone fusion material, said inserterbeing elongate and comprising: a distal end and a proximal end, saiddistal end being releasably attachable to said device, said inserterincluding an actuator at said proximal end and an expansion component atsaid distal end operably coupled to said actuator to cooperativelyengage expansion structure in said device for expanding said device,said inserter including a graft shield projecting from the distal end ofsaid inserter and being of size and configuration to extend into saiddevice, said graft shield being flexible and movable during expansion ofsaid device to provide a barrier to block communication between at leasta portion of said graft chamber and said expansion structure duringexpansion of said device.
 2. The inserter of claim 1, further includingat least one insert movably supported by said inserter for slidableinsertion into said device, said inserter including a driver operablycoupled to said actuator for contacting and driving said at least oneinsert into said device.
 3. The inserter of claim 1, wherein said graftshield is supported at one end in a cantilevered manner with an oppositeend being unsupported and free to flex.
 4. The inserter of claim 3,wherein said graft shield is elongate and generally flat.
 5. Theinserter of claim 4, further including an elongate track having a distalend and a proximal end, said graft shield projecting from the distal endof said track.
 6. The inserter of claim 5, wherein said track isconfigured to linearly support a plurality of inserts for sequentialindividual insertion into said device.
 7. The inserter of claim 5,further comprising an elongate guide pin for releasable connection tosaid device and detachable connection to said track.
 8. The inserter ofclaim 7, further comprising a frame, said frame supporting said actuatoron one side and said track on an opposite side, said actuator defining alower side and said track defining an upper side.
 9. The inserter ofclaim 8, wherein said guide pin is closer to said upper side than saidgraft shield and overlies said graft shield.
 10. The inserter of claim9, wherein said actuator comprises a pair of hand grips, one of which isfixedly secured to said frame and the other of which is pivotallyconnected to said frame.
 11. The inserter of claim 8, wherein saidelongate guide pin has a distal end and a proximal end, said distal endbeing threaded for releasable threaded engagement into said device. 12.The inserter of claim 11, wherein the proximal end of guide pin isprovided with a threaded member for compressing and releasably attachingsaid frame and said track to said device.
 13. The inserter of claim 12,wherein said elongate track comprises a securement feature at the distalend for securing said track to said device.